The effect of 30 μM ebselen or 7.5 mM NAC on intracellular GSH: GSSG ratio in the human CD4+TCC 400–23 when supplemented from a young in vitro age or from a later time point in the in vitro lifespan. A &B denotes the impact of either antioxidant supplemented from a young in vitro age and C &D denotes the impact of these antioxidants when supplemented from the later stages of their in vitro lifespan. The bars indicate the mean ± S.D. Values statistically different from their controls (Student’s t-test, 95% confidence level) are indicated with an asterisk. * p < 0.05 - Significantly higher than the ratio of non-supplemented cells.